On Valleyview, the HW deduces the base of the reserved portion of stolen
memory as being (top - size) and the address field within
GEN6_STOLEN_RESERVED is set to 0. Add yet another GEN6_STOLEN_RESERVED
reader to cope with the subtly different path required for vlv.

v2: Avoid using reserved_base = reserved_size = 0 as the invalid
condition as that typically falls outside of the stolen region,
provoking a consistency error.

Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrj...@linux.intel.com>
Cc: Imre Deak <imre.d...@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_stolen.c | 103 ++++++++++++++++++---------------
 1 file changed, 56 insertions(+), 47 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c 
b/drivers/gpu/drm/i915/i915_gem_stolen.c
index 7cc273e690d0..664afcffc41d 100644
--- a/drivers/gpu/drm/i915/i915_gem_stolen.c
+++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
@@ -185,11 +185,8 @@ static void g4x_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
        DRM_DEBUG_DRIVER("%s_STOLEN_RESERVED = %08x\n",
                         IS_GM45(dev_priv) ? "CTG" : "ELK", reg_val);
 
-       if ((reg_val & G4X_STOLEN_RESERVED_ENABLE) == 0) {
-               *base = 0;
-               *size = 0;
+       if ((reg_val & G4X_STOLEN_RESERVED_ENABLE) == 0)
                return;
-       }
 
        /*
         * Whether ILK really reuses the ELK register for this is unclear.
@@ -197,18 +194,13 @@ static void g4x_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
         */
        WARN(IS_GEN5(dev_priv), "ILK stolen reserved found? 0x%08x\n", reg_val);
 
-       *base = (reg_val & G4X_STOLEN_RESERVED_ADDR2_MASK) << 16;
+       if (!(reg_val & G4X_STOLEN_RESERVED_ADDR2_MASK))
+               return;
 
+       *base = (reg_val & G4X_STOLEN_RESERVED_ADDR2_MASK) << 16;
        WARN_ON((reg_val & G4X_STOLEN_RESERVED_ADDR1_MASK) < *base);
 
-       /* On these platforms, the register doesn't have a size field, so the
-        * size is the distance between the base and the top of the stolen
-        * memory. We also have the genuine case where base is zero and there's
-        * nothing reserved. */
-       if (*base == 0)
-               *size = 0;
-       else
-               *size = stolen_top - *base;
+       *size = stolen_top - *base;
 }
 
 static void gen6_get_stolen_reserved(struct drm_i915_private *dev_priv,
@@ -219,11 +211,8 @@ static void gen6_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
 
        DRM_DEBUG_DRIVER("GEN6_STOLEN_RESERVED = %08x\n", reg_val);
 
-       if ((reg_val & GEN6_STOLEN_RESERVED_ENABLE) == 0) {
-               *base = 0;
-               *size = 0;
+       if (!(reg_val & GEN6_STOLEN_RESERVED_ENABLE))
                return;
-       }
 
        *base = reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK;
 
@@ -246,6 +235,33 @@ static void gen6_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
        }
 }
 
+static void vlv_get_stolen_reserved(struct drm_i915_private *dev_priv,
+                                   resource_size_t *base,
+                                   resource_size_t *size)
+{
+       u32 reg_val = I915_READ(GEN6_STOLEN_RESERVED);
+       resource_size_t stolen_top = dev_priv->dsm.end + 1;
+
+       DRM_DEBUG_DRIVER("GEN6_STOLEN_RESERVED = %08x\n", reg_val);
+
+       if (!(reg_val & GEN6_STOLEN_RESERVED_ENABLE))
+               return;
+
+       switch (reg_val & GEN7_STOLEN_RESERVED_SIZE_MASK) {
+       default:
+               MISSING_CASE(reg_val & GEN7_STOLEN_RESERVED_SIZE_MASK);
+       case GEN7_STOLEN_RESERVED_1M:
+               *size = 1024 * 1024;
+               break;
+       }
+
+       /*
+        * On vlv, the ADDR_MASK portion is left as 0 and HW deduces the
+        * reserved location as (top - size).
+        */
+       *base = stolen_top - *size;
+}
+
 static void gen7_get_stolen_reserved(struct drm_i915_private *dev_priv,
                                     resource_size_t *base,
                                     resource_size_t *size)
@@ -254,11 +270,8 @@ static void gen7_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
 
        DRM_DEBUG_DRIVER("GEN6_STOLEN_RESERVED = %08x\n", reg_val);
 
-       if ((reg_val & GEN6_STOLEN_RESERVED_ENABLE) == 0) {
-               *base = 0;
-               *size = 0;
+       if (!(reg_val & GEN6_STOLEN_RESERVED_ENABLE))
                return;
-       }
 
        *base = reg_val & GEN7_STOLEN_RESERVED_ADDR_MASK;
 
@@ -283,11 +296,8 @@ static void chv_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
 
        DRM_DEBUG_DRIVER("GEN6_STOLEN_RESERVED = %08x\n", reg_val);
 
-       if ((reg_val & GEN6_STOLEN_RESERVED_ENABLE) == 0) {
-               *base = 0;
-               *size = 0;
+       if (!(reg_val & GEN6_STOLEN_RESERVED_ENABLE))
                return;
-       }
 
        *base = reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK;
 
@@ -315,28 +325,18 @@ static void bdw_get_stolen_reserved(struct 
drm_i915_private *dev_priv,
                                    resource_size_t *size)
 {
        u32 reg_val = I915_READ(GEN6_STOLEN_RESERVED);
-       resource_size_t stolen_top;
+       resource_size_t stolen_top = dev_priv->dsm.end + 1;
 
        DRM_DEBUG_DRIVER("GEN6_STOLEN_RESERVED = %08x\n", reg_val);
 
-       if ((reg_val & GEN6_STOLEN_RESERVED_ENABLE) == 0) {
-               *base = 0;
-               *size = 0;
+       if (!(reg_val & GEN6_STOLEN_RESERVED_ENABLE))
                return;
-       }
 
-       stolen_top = dev_priv->dsm.end + 1;
+       if (!(reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK))
+               return;
 
        *base = reg_val & GEN6_STOLEN_RESERVED_ADDR_MASK;
-
-       /* On these platforms, the register doesn't have a size field, so the
-        * size is the distance between the base and the top of the stolen
-        * memory. We also have the genuine case where base is zero and there's
-        * nothing reserved. */
-       if (*base == 0)
-               *size = 0;
-       else
-               *size = stolen_top - *base;
+       *size = stolen_top - *base;
 }
 
 int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
@@ -369,7 +369,7 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
        GEM_BUG_ON(dev_priv->dsm.end <= dev_priv->dsm.start);
 
        stolen_top = dev_priv->dsm.end + 1;
-       reserved_base = 0;
+       reserved_base = stolen_top;
        reserved_size = 0;
 
        switch (INTEL_GEN(dev_priv)) {
@@ -389,8 +389,12 @@ int i915_gem_init_stolen(struct drm_i915_private *dev_priv)
                                         &reserved_base, &reserved_size);
                break;
        case 7:
-               gen7_get_stolen_reserved(dev_priv,
-                                        &reserved_base, &reserved_size);
+               if (IS_VALLEYVIEW(dev_priv))
+                       vlv_get_stolen_reserved(dev_priv,
+                                               &reserved_base, &reserved_size);
+               else
+                       gen7_get_stolen_reserved(dev_priv,
+                                                &reserved_base, 
&reserved_size);
                break;
        default:
                if (IS_LP(dev_priv))
@@ -402,11 +406,16 @@ int i915_gem_init_stolen(struct drm_i915_private 
*dev_priv)
                break;
        }
 
-       /* It is possible for the reserved base to be zero, but the register
-        * field for size doesn't have a zero option. */
-       if (reserved_base == 0) {
-               reserved_size = 0;
+       /*
+        * Our expectation is that the reserved space is at the top of the
+        * stolen region and *never* at the bottom. If we see !reserved_base,
+        * it likely means we failed to read the registers correctly.
+        */
+       if (!reserved_base) {
+               DRM_ERROR("inconsistent reservation %pa + %pa; ignoring\n",
+                         &reserved_base, &reserved_size);
                reserved_base = stolen_top;
+               reserved_size = 0;
        }
 
        dev_priv->dsm_reserved =
-- 
2.16.2

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